Field
The presently disclosed subject matter relates to an optical touch panel.
Description of the Related Art
In FIG. 8, which illustrates a first prior art optical touch panel (see: FIGS. 1(a), 1(b), 1(c) and 1(d) of EP2088499 A1, FIG. 2 of US2012/0200537A1), a glass substrate 1 for defining a display surface also serves as an upper glass substrate of a liquid crystal display (LCD) device, for example. Also, provided on the glass substrate 1 are two substrates 2X-a and 2X-b along a Y-direction at opposite sides to each other. Further, provided on the glass substrate 1 are two substrates 2Y-a and 2Y-b along an X-direction at opposite sides to each other.
In addition, X-direction light emitting elements such as light emitting diode (LED) elements 3X-a are equidistantly arranged on the substrate 2X-a, and X-direction light receiving elements such as phototransistor elements 3X-b are equidistantly arranged on the substrate 2X-b. The LED elements 3X-a oppose respective ones of the phototransistor elements 3X-b.
Similarly, Y-direction light emitting elements such as LED elements 3Y-a are equidistantly arranged on the substrate 2Y-a, and Y-direction light receiving elements such as phototransistor elements 3Y-b are equidistantly arranged on the substrate 2Y-b. The LED elements 3Y-a oppose respective ones of the phototransistor elements 3Y-b.
Light LX1 emitted from one of the LED elements 3X-a passes over the display surface to reach one of the phototransistor elements 3X-b. In this case, when an object such as a finger A is present on the display surface to intercept the light LX1, the light LX1 does not reach the one of the phototransistor elements 3X-b. Thus, it can be determined whether or not the finger A is present on a coordinate X1 of the light LX1 by whether or not the one of the phototransistor elements 3X-b detects the light LX1.
Similarly, Light Ly1 emitted from one of the LED elements 3Y-a passes over the display surface to reach one of the phototransistor elements 3Y-b. In this case, when the finger A is present on the display surface to intercept the light Ly1, the light Ly1 does not reach the one of the phototransistor elements 3Y-b. Thus, it can be determined whether or not the finger a is present on a coordinate Y1 of the light LY1 by whether or not the one of the phototransistor elements 3Y-b detects the light LY1.
Thus, it is possible to determine whether or not the finger A is located at a position (X1, Y1) by whether neither of the lights LY1 and Ly1 are detected.
In the optical touch panel as illustrated in FIG. 8, however, even if other objects such as fingers B, C and D, whose positions are (X1, Y2), (X2, Y1) and (X2, Y2). respectively, are present simultaneously with the finger A, the fingers B, C and D cannot be detected. That is, since propagating directions of lights LX1 and LX2 are perpendicular to those of lights LY1 and LY2, the fingers B and C are shadowed by the finger A, and the finger D is shadowed by the fingers B and C. Thus, it is impossible to carry out a multiple touch operation using two or more fingers simultaneously.
In FIG. 9, which illustrates a second prior art optical touch panel, the LED elements 3X-a, the phototransistor elements 3X-b, the LED elements 3Y-a and the phototransistor elements 3Y-b of FIG. 8 are replaced by light emitting and receiving packages 3X′-a, light emitting and receiving packages 3X′-b, light emitting and receiving packages 3Y′-a and light emitting and receiving packages 3Y′-b, respectively. Each of the light emitting and receiving packages 3X′-a, 3X′-b, 3Y′-a, and 3Y′-b has the same configuration formed by a light emitting element such as an LED element 31 and a light receiving element such as a phototransistor 32 which are laterally and closely arranged. Thus, each of the fingers A, B, C and D can be individually detected by a reflective photo-intercepting technology.
For example, light LX1 emitted from the LED element 31 of one of the light emitting and receiving packages 3X′-a is reflected by the finger A to reach the phototransistor element 32 thereof, and also, light LY1 emitted from the LED element 31 of one of the light emitting and receiving packages 3Y′-a is reflected by the finger A to reach the phototransistor element 32 thereof. Thus, it can be determined whether or not the finger A is located on a position (X1, Y1) by whether or not the reflected lights LX1 and LY1 are both present simultaneously.
In addition, light LX2 emitted from the LED element 31 of one of the light emitting and receiving packages 3X′-b is reflected by the finger B to reach the phototransistor element 32 thereof, and also, light LY1, emitted from the LED element 31 of one of the light emitting and receiving packages 3Y′-a is reflected by the finger B to reach the phototransistor element 32 thereof. Thus, it can be determined whether or not the finger B is located on a position (X2, Y2) by whether or not the reflected lights LX2 and LY2 are both present simultaneously.
Further, light LX3 emitted from the LED element 31 of one of the light emitting and receiving packages 3X′-a is reflected by the finger C to reach the phototransistor element 32 thereof, and also, light LY3 emitted from the LED element 31 of one of the light emitting and receiving packages 3Y′-b is reflected by the finger C to reach the phototransistor element 32 thereof. Thus, it can be determined whether or not the finger C is located on a position (X3, Y3) by whether or not the reflected lights LX3 and LY3 are both present simultaneously.
Still further, light LX4 emitted from the LED element 31 of one of the light emitting and receiving packages 3X′-b is reflected by the finger D to reach the phototransistor element 32 thereof, and also, light LY4 emitted from the LED element 31 of one of the light emitting and receiving packages 3Y′-b is reflected by the finger D to reach the phototransistor element 32 thereof. Thus, it can be determined whether or not the finger D is located on a position (X4, Y4 by whether or not the reflected lights LX4 and LY4 are both present simultaneously.
Thus, even if X1=X2, the finger B is not shadowed by the finger A. Also, even if Y3=Y1, the finger C is not shadowed by the finger A. Further, even if X4=X3 and Y4=Y2, the finger D is not shadowed by the fingers B and C.
In the optical touch panel as illustrated in FIG. 9, however, in each of the light emitting and receiving packages 3X′-a, 3X′-b, 3Y′-a and 3Y′-b, when the light distributing characteristics of the LED element 31 and the light distributing characteristics of the phototransistor element 32 are deviated, the noise of the phototransistor element 32 would be increased. For example, when the optical axis of the LED element 31 of one of the light emitting and receiving packages is shifted horizontally in the right or left direction, so that the light distributing characteristics of this LED element 31 are deviated as shown in FIG. 10, light emitted from the LED element 31 and reflected by a finger would be received by the phototransistor elements of its neighboring light emitting and receiving packages to increase the noise thereof.